Our invention relates to apparatus for preparing human bone to receive an implanted prosthesis, and particularly to receive a femoral hip prosthesis.
Various types of femoral hip prostheses are known and are used for surgical reconstruction of the hip joint. In general, these prostheses comprise a ball-shaped head mounted at an anatomical angle on a stem. The stem can be thrust into the medullar canal of the femur to mount the prosthesis at a resected surface of the femur. Many of these prostheses have collars near their proximal end which rest upon the resected surface. Both permanently attached collars and replaceable collars are known. In some cases, however, a patient's femur may have insufficient bone mass near the proximal end of the femur to support the collar or, during revision surgery when a second operation is necessary, additional bone may be removed. To restore a prosthesis to an anatomically correct position, the prosthesis would protrude further out of the remaining femur, leaving a gap between the collar and the resected surface of the femur. Spacers or other apparatus have been proposed to fill this gap. Such a femoral hip prothesis with spacer is described in U.S. patent application 08/101,421, filed Aug. 3, 1993, an application assigned to Intermedics Orthopedics, Inc.
We have found that it is important to accurately prepare the proximal surface of the femur to receive such a femoral hip prosthesis. In particular, it is sometimes necessary to mill away a portion of the femur medially and proximally on the femur, below an area which is normally covered by a collar. This area is difficult to reach during the revision operation.